There’s a particularly unusual difficulty with creating an effective adult comedy that wants to balance the line between screwball and sensitivity, between profane and profound. The great ones will perform that juggling act carefully yet effortlessly, demonstrating humor that combines the awkwardness of human weakness with just the right amount of vulgarity to make it both real and funny, while being cautious not to teeter into Scary Movie/gross-out land, beating the same dull jokes into the ground relentlessly.

We’re The Millers tries very hard to balance that line, and succeeds more than it fails. It succeeds particularly in its comedic goals, even if its attempts at sincerity sometimes feel a little flat. Jason Sudeikis plays David, a medium-time pot dealer who casually and lazily smarms his way through life while never stopping to realize how pathetic he might actually be. When he becomes indebted to an loopy,affable-yet-psychotic white collar drug kingpin (Ed Helms. Yeah, you read that right), he’s forced to assemble a fake family to head down to Mexico and mule some dope back over the border in order to wipe the slate clean and keep himself breathing. He signs on a down-on-her-luck stripper named Rose (Jennifer Aniston), Casey (Emma Roberts), a homeless teenage reprobate, and Kenny, the goofy, wide-eyed simpleton that lives in his building (Will Poulter). Together, they form the Millers, a fictional family with little in common other than no real purpose in their lives and a need for quick cash.

If the plot sounds ridiculous, well, it is — deliciously so. It’s reminiscent of 2011’s Horrible Bosses in that it assembles a hapless team under madcap circumstances, and then simply hurls them through a gamut of increasingly nutty situations while along the way they somehow become better people for it. Sudeikis plays a similar brand of smug a-hole here, yet there’s a wry likability to him that makes his particular brand of insincere jackassery strangely enjoyable. It’s that obnoxious persuasiveness that brings the group together, but it’s also what leads to the film’s continuous, ludicrous hijinks. It begins when they realize that they’re being forced to deliver way more dope than expected, and continues as they encounter uncomfortably friendly border guards (Luis Guzman), a murderous drug dealer (Tomer Sisley), not to mention a frustratingly wholesome family comprised of Nick Offerman, Kathryn Hahn, and Molly Quinn.

The film works because there really is some excellent chemistry among the leads and supporting players, particularly Sudeikis and Aniston. Sudeikis can pretty much play this role in his sleep, but Aniston, in a toned-down, less malicious version of her hypersexualized Horrible Bosses character, really shines once again. Her post-“Friends” career hasn’t been entirely smooth, but she seems to have found a niche in playing brassy, ballsy women who take little sh*t but give plenty back. Here she’s a solid foil for Sudeikis, and their contentious-yet-charming relationship works better than one might expect. Roberts and Poulter round out the foursome nicely, playing opposite ends of the teenage spectrum off of each other with a scathing cleverness by Roberts and Poulter’s loopy sweetness. As for Offerman and Hahn, I expected for their shtick to grow old, yet it actually worked well as a contrast to the dysfunctional wickedness of the fictional Millers.

The humor of the film is crude and vulgar and often hilarious. In fact, it’s at its best when co-writers Bob Fisher and Steve Faber and director Rawson Thurber throw caution to the wind and takes a few chances. When Kenny gets bitten in the balls by a tarantula, it’s not that rather obvious plot device that makes the scene work, but rather both the reactions and the twisted fashion that each of the other three react (Roberts should win some sort of award for her brilliant reaction shots). When Aniston and Sudeikis are dealing with Offerman and Hahn, it’s not the obvious, somewhat hokey contrasts that make the scenes succeed, but instead the biting dialogue between Sudeikis and Aniston, paired with the genuine-feeling charm of Offerman’s family that is so very different.

When the humor misses the mark is when it resorts to convention and obviousness. The now (in)famous stripping scene isn’t particularly effective, not because there is any problem with Aniston (either in physicality or performance), but because it’s just so obvious and lame. It would have been one thing if each of the characters had to, at some point, exercise a particular brand of skills in order to get them out of a bind. Instead, it’s only Aniston who has to do so, and as a result, the gag feels cheap and a bit exploitative. Similarly, the dialogue occasionally switches to a more overt, less dry style that feels less subversive and more deliberately crowd pleasing (particularly things like cliched Willie Nelson references and soon-to-be dated Bane imitations, which felt tired in the trailer and no less so in the larger context).

The second of the film’s occasional stumbles is its attempts at sincerity. The third act is where the threads are supposed to tie together, where the Very Important Lessons are learned, and where this unlikely band of con artists are supposed to become more of a fully realized family. It never quite gels, instead feeling less organic than when they were busy serving heaping portions of snark and learning each other’s vulnerabilities. It was those formative moments, both when they’re at each other’s throats but also when they’re finding (and often empathizing with) each other’s weaknesses, that the cast works best together. The saccharineness of the final third often brought the film’s blistering momentum to a halt, however.

However, neither of those issues should make you avoid the film. We’re The Millers has some genuinely hilarious moments, and the first two thirds is a consistently funny, bawdy adventure that only stumbles when it inexplicably pulls its punches. And while the back third of it sometimes staggers under the weight of its own less-than-believable sincerity, the more honest charm of Offerman’s family does somewhat counteract that. Yet it’s ultimately Sudeikis, Aniston, and their viciously vulgar little drug-muling Brady Bunch imposters that own the movie and provide the kind of twisted humor that makes it worthwhile.